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New Chain slipping

aidsoaidso Posts: 493
edited April 2017 in MTB workshop & tech
Would anyone be able to suggest what could be wrong here.
Brand new large chain ring (same size and brand as last) and new chain.
In the largest cog at front and largest at cassette, the chain is riding on top of the front teeth rather than in the grooves and therefore keeps dropping. The rear is also skipping in the top 3 cogs


  • cougiecougie Posts: 22,512
    You're not meant to use large large. Is the chain too short like this?
  • aidsoaidso Posts: 493
    Yeah I know about the cross-chaining problem but that to me is a bit of a cop-out. Ive had this bike nearly 3 years and have managed to get into that gear ratio (new chains etc along the way)- now all of a sudden its a problem.
    I had the following theories:
    a) The chain is cut too short
    b) The new chain ring is the wrong way round
    c) The cassette is worn

    Now Ive swapped the wheel for a different one - not quite a new cassette, but certainly not hugely worn - and it does the same thing. So I'm left with options a or b unless its something else?
  • kajjalkajjal Posts: 3,380
    If it is slipping on the rear cassette sounds like it is worn in a few gears and needs replacing.
  • FishFishFishFish Posts: 2,152
    ...tried cleaning and lubricating the cable sheaths..?
    ...take your pickelf on your holibobs.... :D

    jeez :roll:
  • fenixfenix Posts: 5,437
    Not sure what the cables have to do with it ?

    That chain not sitting on the teeth is weird.

    Can you place it properly on them ?

    The too short chain could be it - but you'd be able to see this from how tight the derailleur is pulled.

    If the chain ring is the same as last time - have you bought the right chain ? There are two standard aren't there ?
  • aidsoaidso Posts: 493
    I've brought it back to the shop for their expertise - they are as puzzled as I am (they fitted it :O)
    Same chain and same ring, but it looks like the ring is too far out - maybe a spacer in the wrong place?
  • The RookieThe Rookie Posts: 27,748
    Riding big/big will cause more of an issue with a new chain than and old as its stiffer laterally and therefore resist the twist from the chain axis to the front ring axis with greater force. A worn chain is much more flexible and easier to bend.

    Just choose the gears properly I would suggest.
  • robertpbrobertpb Posts: 1,866
    You can see in the picture that the chain is being stressed sideways far too much, so the chain will try to straighten as it has a mechanical load sideways, simples.
    As Rookie has stated above.
    Now where's that "Get Out of Crash Free Card"
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